This is a multi-disciplinary project aimed at studying the etiology and pathogenesis of hyaline membrane disease to try to better understand some of the mechanisms through which therapy is effectual, and to look at long-term outcome in infants who have had the disease. Etiology of HMD. Steroid biosynthesis and metabolism during pregnancy and during normal and premature parturition. Studies of the enzymes active in lipid synthesis in developing lung. These studies will be closely coordinated with studies of the biochemical and anatomical development of the fetal lung. Pathogenesis of HMD. Studies of the physiological, biochemical and pathological effects of intrauterine stress which is capable of inducing HMD in fetal lambs will continue utilizing chronic intrauterine catheters. Studies of the recovery process of HMD will continue on infants dying late in the disease. Studies relating to massive intracranial bleeding and associated etiological factors will be carried out utilizing chromium 50 red cell tagging and evoked EEG potential. The incidence and effects of hypovolemia will be continued using chromium 51 tagged red cells. Management of HMD. The Kolobow membrane lung is being evaluated in lambs with induced HMD as a method of oxygenation and CO2 removal until spontaneous recovery occurs. The use of end-expiratory positive pressure versus continuous external negative pressure around the thorax is being evaluated in infants with serious HMD by blood gases, ease of oxygenation and by changes in trans-thorastic impedance measurements. Studies of the effects of total parenteral alimentation on the recovery rate, growth patterns and long-term physical and intellectual development of infants with HMD and small prematures will continue. Sequelae of HMD and its Complications. The effects of long-term separation on the attitudes and behavior of parents of high-risk infants will be continued. There will be a continuation of long-term sequential somatic, psychological and intellectual developmental studies on children who had HMD as newborn infants. Pulmonary function studies will continue.